Hollow wall anchor bolt



y 968 LA ROY B. PASSER 3,381,566

HOLLOW WALL ANCHOR BOLT Filed May 6, 1966 PM? 2 g M6 54 25 24 35 20 INVENTOR LA ROY B. PASSER ATTORNEYS United States Patent f ABSTRACT 0F THE DISCLOSURE A hollow wall anchor bolt constituting a point tipped tubular sleeve having an internally threaded forward end and a headed rear end, the length of the sleeve between the ends being broken up by a few spiral slots. A screw is threaded into the forward end of the sleeve, the direction of the threads being opposite to the direction of the spiraling of the slots so that when the sleeve is in serted through a wall so that the major portion of its length protrudes into the hollow behind the wall and the screw thereafter is tightened, the legs between the slot will balloon into a cloverleaf configuration pressed against the internal surface of the wall.

The present invention relates to an anchor bolt for a hollow wall, the bolt being of the type which is expandable in the open area within the wall.

It is a primary object of my invention to provide a new and improved expandable-type anchor bolt for emplacement into a hollow wall, the anchor bolt being so configured that it can be quickly and easily driven into the wall with but a few strokes of a hammer, after which the bolt can be easily and quickly secured in the hollow wall.

It is a further object of my invention to provide a hollow wall expandable anchor bolt of the character described which after its attachment to a hollow wall, functions as a female element to receive and mate with a male element, said male element being removable therefrom as often as desired, with the female element remaining fixed in the wall.

It is still a further object of my invention to provide a hollow wall expandable anchor bolt of the character described which expands in the open area within the wall to a configuration which resembles the shape of multiple radial petals, the aforesaid configuration securing the anchor bolt to the wall more firmly than previous expandable anchor bolts, and such configuration offering greater resistance to being pulled out through the wall than previous expandable anchor bolts.

It is still another object of my invention to provide a hollow wall expandable anchor bolt of the character described which is simple in construction, which may be mass produced at low cost and which may be used especially conveniently by do-it-yourself home owners and apartment dwellers who are" relatively unskilled in the mechanical arts.

These and various other objects and advantages of my invention will in part be pointed out hereinafter and in part will become apparent to the reader in the following description.

My invention accordingly consists in the features of construction, combinations of elements, and arrangements of parts which will be exemplified in the wall anchor bolt hereinafter described and of which the scope of application will be indicated in the appended claims.

In the accompanying drawings in which is shown one of the possible embodiments of my invention,

FIG. 1 is a side elevational view of my hollow wall expand-able anchor bolt, the anchor bolt being illustrated in a position with its male and female components mated and the bolt ready to be driven into a hollow wall;

331,566 Patented May 7, 1968 FIG. 2 is an enlarged axial cross-sectional view of the anchor bolt of FIG. 1, the anchor bolt having been driven into the wall but being shown prior to being brought to expanded condition;

FIG. 3 is a perspective view of the forward portion of the anchor bolt located in the open area within a hollow wall and showing the forward portion in partially expanded condition;

FIG. 4 is a View similar to FIG. 3 but showing the anchor bolt in fully expanded position with the male component withdrawn from the female component; and

FlG. 5 is a cross-sectional axial view taken substantially along the line 5-5 of FIG. 4.

In general, and in accordance with the teaching of my invention, I provide an anchor bolt for particular use with hollow walls, that is, a wall having an open though hidden area within it. Typically, such walls are formed from gypsum blocks or from spaced parallel sheets of plasterboard. My hollow wall anchor bolt is of the expandable type, that is, the type which passes through a panel of the wall, expands in the open space within the wall and grips the wall panel between a portion thereof abutting the exposed face of the said wall and said expanded portion.

My anchor bolt includes an axially elongated essentially constant diameter hollow sleeve having at its rearward end an enlarged flange. Said flange prevents the anchor bolt from entering into the wall beyond the flange and said flange is forced against the exposed face of the wall when the anchor bolt is in its fully expanded condition.

As has been mentioned, the sleeve is hollow and it is threaded internally only at its forward end, the end opposite to the end at which the flange is fixed. The aforesaid hollow sleeve constitutes the female member of my anchor bolt.

A male member of my anchor bolt constitutes an elongated headed screw. The internal diameter of the sleeve and the external diameter of the screw are dimensioned so that the screw can be readily and freely inserted therein and will engage the sleeve only at the internally threaded forward end of said sleeve. The tip of the screw is pointed and when the screw is fully inserted into and threadedly mated with the sleeve, the tip of the screw protrudes from the sleeve. My hollow wall anchor bolt thereby presents a pointed leading tip and a trim outline which enables the bolt to be easily driven into a hollow wall as by the use of a hammer, until the flange of the sleeve abuts the exterior face of the wall and the forward portion of the anchor bolt is situated in the open area within the wall.

The sleeve of my wall anchor bolt is characterized by a small number of uniformly spaced spiralling slits or slots which divide the sleeve into a small number of spiralling legs. By the term small number is meant two, three or more but less than nine slots and legs. Said spiralling slots and legs run substantially the entire length of the wall anchor bolt from the flange to immediately short of the threaded portion of the sleeve. The slots and legs encircle the sleeve and pass through an arc of from about 270 to about 540. The pitch of the legs and slots rotates in a direction opposite to the rotation of the pitch of the screw.

The wall anchor bolt with the screw sheathed by the sleeve is driven into a wall so that the sleeve penetrates the front panel of the wall and the forward portion of the sleeve is in the hollow wall area. The screw is then rotated so that the head of the screw bears against the rear of the sleeve so as to draw the internally threaded forward end of the sleeve toward the flange. The spiralling legs of the sleeves, as the forward end of the sleeve moves toward the rear end of the sleeve, balloon radially outwardly and as the screw continues to be rotated and as the end of the sleeve closely approaches the hidden face of the hollow wall, the legs assume a looped multiple radial petal configuration. The petals lie flattened against the inner face of the penetrated panel. Said configuration combined with the flange on the exposed wall surface very securely grip the hollow wall panel therebetween, and prevent any subsequent removal of the anchor bolt from said wall. The aforesaid multiple radial petal configuration is found to have greatly improved holding power as compared to other expanding type wall anchor bolts which conventionally assume a simple cross configuration after they have been expanded. After the wall anchor bolt is fully expanded, the screw may be withdrawn, placed through an aperture in any object to be hung on the wall, and then rethreaded into the drawn-up sleeve. Of course, the sleeve of the anchor bolt is now firmly and securely located in place, and the screw may be withdrawn and replaced as many times as desired.

Referring now in detail to the drawings, the reference numeral denotes an anchor bolt constructed in accordance with my invention. My anchor bolt has its best use with hollow walls, i.e., a wall W having an empty hidden space S within it. Such walls may be typically formed from plaster, plasterboard, sheetrock panels and the softer woods. The anchor bolt 1% is best formed from a material which is deformable and inelastic, especially when in sheet form, a malleable alloy or steel sheet being suitable.

The anchor bolt it) includes two mating components, to wit, a female component which constitutes an elongated hollow tubular sleeve 12 and a male component which constitutes an elongated screw 14.

The sleeve has at one end thereof a circular annular flat flange 16 which lies in a plane perpendicular to the axis of the sleeve. The flange is in one piece with the remainder of the sleeve 12 and has an outside diameter substantially greater than the remainder of the sleeve. The flange 16 has mounted thereon a pair of forwardly protruding triangular pointed teeth which are formed as by notching the flange 16. When the flange 16 abuts the exposed face of a wall, the teeth 1%; dig into the wall and prevent rotation of the flange 16 and the remainder of the sleeve 12.

The sleeve 12, except at its forward or leading end, is essentially of uniform circular interior and exterior diameter and said sleeve i substantially axially elongated. The sleeve has a hollow cylindrical wall 20 which defines an elongated cylindrical hollow open ended central bore 22.

The sleeve has a leading end 24 which is internally threaded as at 25, this being the only portion of the bore 22 which is threaded and said portion is of a slightly smaller internal diameter. Further, the exterior surface of the leading end 24 is frusto-conical, and it tapers towards the front.

The screw 14 is, as has been stated, the male component of my anchor bolt 10, and said screw includes an enlarged head 26 (larger than the bore 22) with a transverse exposed slot 28 therein to accommodate the tip of a screw driver. The head of the screw will abut the rear of the sleeve, i..e., the area of the flange surrounding the bore, when the screw is inserted into the sleeve from the rear to the front thereof. The screw includes an elongated threaded shank 39 which is fixed to the head 26 and which has an external diameter which is less than the diameter of the bore except for the internally threaded portion of the bore which mates with the screw. Thus, it will be understood that while the screw readily and freely fits into the major length of the bore 22, said screw threadedly mates only with the internally threaded forward portion of the sleeve .12. It will be seen that, as best shown in FIG. 2, when the screw 14 is fully inserted into the sleeve, with a forward portion thereof mating with the internally threaded portion of the sleeve, the screw and the sleeve are co-axial and the length of the screw from its 4; head to its tip is longer than the sleeve from its flange to its leading end 24.

The screw 14 has a leading pointed tip 34 which protrudes from the leading end 24 of the sleeve, when said screw is fully threaded into said sleeve. Said pointed tip 34 is frusto-conical and has a slope which matches the slope of the leading end 24 so that when said components are assembled, the leading end 24 of the sleeve smoothly fares into the pointed tip 34 of the screw and no obstruction is presented to stop the sleeve with the screw therein from readily piercing a wall W, when so driven, as by a hammer.

The sleeve 12 is further characterized by the provision of a small number of spiralling slots 36 which divide the wall 20 into a small number of spiralling legs 38. By the term small number is meant two, three, four or five legs; in any case less than nine legs. The slots 36 and the legs into which the slots divide the wall 20 run intermediate the ends of the sleeve from a point immediately to the rear of the leading end 24- of the sleeve 12 to a point immediately forward of the flange 16. With this location for the slots, there are two circumferential bands formed, one at either end of the sleeve, one of said bands do constituting the leading end 24 and the other of the bands 42 being at the rear of the sleeve 12. It will be appreciated that the provision of the bands 40, 42; leaves areas at either end of the sleeve which are not weakened by slots so that the strength of the sleeve is not impaired at these critical areas.

The slots 36 are of uniform and of a relatively narrow circumferential width as compared to the width of the legs 38, the width of a slot exemplificatively being about A or of the width of any leg. The slots 36 as well as the legs 38 are uniformly spaced about the circumference of the sleeve 12. In the embodiment illustrated, there are four slots shown, which in turn divide the sleeve into four legs, there being a slot at each of the 360 circumference of the sleeve. The slots and legs are helical with respect to sleeve, and they follow a rotative path or sweep about the axis of the sleeve which has an arc of from about 270 to about 540", with a path of about 360 are shown in the drawings.

It is critical to my invention that the spiral of the slots and legs twists in a certain direction with respect to the spiral of the threads of the shank of the screw 14. More particularly, the spiral of the legs must twist in a direction opposite to the spiral of the screw threads. In the drawings, the screw thread has a conventional righthand spiral progressing from its head to its tip, while the legs and slots have a left-hand spiral from the flange 16 to the leading end 24.

My wall anchor bolt is illustrated in FIG. 1 in position ready to be driven into wall W. The screw is fully threaded into the sleeve, the pointed tip 34 of the screw protrudes from the front of the bolt and fares into the leading end 24 of the sleeve and the head of the screw abuts the flange 16. The anchor bolt thus presents a pointed tip and trim body which carries no obstruction to a smooth entry. The bolt is driven into a wall, leading end first, by hitting the head 26 of the screw with a hammer. No hole need be formed prior thereto, but rather the bolt pierces the wall and forms its own hole. If desired, a hole can be preformed to receive this bolt. The head can receive the taps of the hammer without failure and the screw shank reinforces the sleeve 12 so that the bolt passes into a wall without deformation. The bolt is driven until the flange 16 abuts the exposed face of the wall with the teeth 18 biting into the exposed wall surface and preventing subsequent rotation of the sleeve with respect to the wall W. In this condition, the forward and major portions of the sleeve and the screw are located in the open area within the wall. The dimensions of the bolt with respect to any wall panel thickness with which it is to be properly utilized are such that the hidden internal face of the wall intersects the sleeve intermediate the bands 40, 42, that is, between the ends of the slots and legs. This is necessary for a proper pracitice of my invention. Desirably the said wall face intersects the sleeve close to the rearward end of the slots and legs so that the major portions of the slots and legs are located in the open space within the Wall.

The screw 14 is then rotated with respect to the sleeve, the sleeve being held stationary by the teeth 18 for this purpose. Since the head of the screw bears against the flange, the rotation of the screw causes the mating internally threaded end 24 of the sleeve to ride rearwardly on the screw threads and to draw up toward the flange 16. As the end 24 is pulled toward the flange, considerable compressive force is applied to the legs, buckling the legs outwardly. FIG. 3 illustrates my anchor bolt partially drawn up by the screw, and it will be observed that the legs have begun to deform by ballooning (expanding) outwardly, each leg spiralling and moving radially away from the sleeve axis. Because the ends of the legs are spaced angularly apart, e.g., from between about 270 to about 540, the legs form petals as they balloon. The rearward portions of the legs (in the open space) are expanded further outwardly than the frontward portions thereof. Further, the legs are twisted with respect to the hidden interior face of the Wall and present their clockwise edges to the said face (looking from front and rear.)

Continued rotation of the screw in the same direction draws the back of the leading end 24 against the hidden face of the wall (see FIGS. 4 and 5) and each leg has formed an expanded wide petal-like loop, the loops i.e., petals overlapping at their bases and each loop at its center being spaced angularly in the illustrated form about 90 from the flanking loops so that the legs as a whole have a multiple radial petalled configuration. Because of the opposite spiral of the legs as compared to the thread of the screw, the angular spacing between the ends of the legs is reduced but the legs in their final deformed condition are still ballooned and collapsed in the shape of loops. The configuration shown has four petals since there are four legs formed in the sleeve, and a sleeve having a greater or lesser number of legs will have a correspondingly greater or lesser number of radial petals. As has been mentioned, the legs of the bolt illustrated in the drawings have a sweep of about 360 and, as best seen in FIGS. 4 and 5, in their final form the ends of the legs are spaced about 180 apart. Each loop has an edge (rather than a broad face thereof) pressed into the hidden wall face. Moreover, the loops lie in a plane generally perpendicular to the sleeve axis and the loops are flattened against the internal face of the wall. As has been said, the bases B of the loops overlap, with the loops being interleaved in shingle fashion. By shingle fashion, is meant that each loop has the base portion of one of its sides passing rearwardly of the base portion of the adjacent side of one flanking loop and said loop has the base portion of its other side passing forwardly of the base portion of the adjacent side of its other flanking loop. The exact shape of the configuration will depend on the number of slots and legs, the wall panel thickness relative to the axial length of the legs and the pitch of the legs. The anchor bolt securely grips the wall between its flange 16 and the expanded multi-radially-petalled leg configuration C. The screw can then be counter-rotated and withdrawn from the sleeve, placed through an aperture in an article, and then placed into and rethreaded with the sleeve. This may be done as often as desired, the sleeve always remaining stationary in the wall to receive the screw.

My anchor bolt has extraordinary staying power in a wall. This is due in part to the fact that the legs 38 when fully expanded have edges which press into the back interior face of the wall panel within the hollow wall. This prevents any rotation of the sleeve with respect to the wall, should the teeth 18 be ineffective for this purpose. It will be appreciated that anchor bolts of conventional design often work their way out of a panel by rotating and grinding a larger hole, or loosening the wall material which surrounds the bolt. My anchor bolt by pressing and biting into the interior face of the wall panel prevents such movement.

The edges of the legs penetrate into the back interior face of the wall to a degree depending in part upon the softness of the material from which the back of the wall is formed and in part upon the force with which the screw 14 is tightened. A substantial segment of the clockwise (looking from front to rear) edge of each leg cuts into said back face and the further the screw is tightened, the more firmly the sleeve grips the wall between the flange 16 and the configuration C of its legs. The segment of each leg which does not have an edge biting into the back face of the wall panel crosses another loop at the base of such loop.

I further desire to point out that when the legs are fully expanded, as best seen in FIGS. 3 and 4, essentially the entire length of each leg (the length of each leg except where each leg overlaps and is forward of another leg) is presented to the back face of the wall panel. For my anchor bolt to be loosened from a wall, a core having a diameter as large as the outside diameter of the configuration C would have to be pulled out of the wall with the bolt, this being practically impossible. This is in contrast to the simple cross configuration which most other expandable wall anchor bolts assume in the open space within a wall. This cross configuration is attained when in the course of expanding, the legs of such anchor bolts fold on themselves and radiate linearly (at intervals if as usual there are four slots). My multipetalled looped configuration presents a much larger area which contacts the back face of the panel when the bolt is expanded. This larger area is achieved by the said configuration, and not by the addition of material.

Thus it will be seen that I have provided a hollow wall anchor bolt which achieves the several objects of my invention and which is well adapted to meet the conditions of practical use.

As various possible embodiments might be made of the above invention and as various changes might be made in the embodiment set forth, it is to be understood that all matter herein described or shown in the accompanying drawings is to be interpreted as illustrative and not in a limiting sense.

I claim:

1. An expandable anchor bolt securable in a hollow wall and comprising:

(a) an elongated hollow tubular sleeve formed from a deformable inelastic material,

(b) a protuberant flange formed at the rear of the sleeve,

(c) the sleeve having an internally threaded forward portion,

(d) a small number of spiralling slots formed in the sleeve intermediate the ends thereof and dividing the sleeve into a like number of spiralling legs, the widths of the slots being small in relation to the widths of the legs,

(e) the forward portion of the sleeve, including a substantial portion of the slots and legs, being dimensioned to be located in the open area in the hollow wall,

(f) the slots and legs following a spiralling path having a circumferential sweep of from between about 270 to about 540,

(g) an elongated screw having an enlarged head and insertable into the sleeve from the rear to the front thereof and mateable with the internally threaded portion of the sleeve.

(h) the spiral of the threads of the screw twisting in a direction opposite to the twist of the spiral of the slots,

(i) whereby when sleeve is inserted into a hollow wall and the screw is engaged with the threaded portion of sleeve and the head of the screw abuts the rear of the sleeve, upon further rotation the forward end of the sleeve is drawn toward the flange and the legs balloon in the open space in the hollow wall into an enlarged looped radially multipetalled configuration With the loops flattened against the interior face of the hollow wall and with the edges of the loops biting into the hidden face, the configuration against said face of the hollow wall and the flange against the exposed face of the wall gripping the wall therebetween and thereby securing the sleeve to the wall, and the screw being subsequently removable from the sleeve and thereafter remateable with the sleeve.

2. An expandable anchor bolt as set forth in claim 1 wherein the screw threads have a conventional right hand twist and the sleeve has a left hand twist.

3. An expandable anchor bolt as set forth in claim 2 wherein there are four slots and four legs, said slots and legs twisting through about a 360 are.

4. An expandable anchor bolt as set forth in claim 1 wherein the interior diameter of the sleeve, except at its internally threaded portion, is larger that the outside diameter of the shank of the screw.

5. An expandable anchor bolt as set forth in claim 1 where the loops are spaced substantially equiangularly apart and each loop has portions forward of a portion of a loop on one side thereof and rearward of a portion of a loop on the other side thereof.

References Cited UNITED STATES PATENTS 2,104,496 1/ 1938 Schaefer 85-85 2,538,601 1/1951 Taylor et a1. 8571 2,918,841 12/1959 Poupitch 85--71 3,143,915 8/ 1964 Tendler 8571 FOREIGN PATENTS 608,218 9/ 1948 Great Britain. 863,130 3/1961 Great Britain.

EDW'ARD C. ALLEN, Primary Examiner. 

